1. Field of the Invention
The present invention relates to compositions including selected strains of Pseudomonas bacteria having the ability to degrade halogenated aromatic compounds. The invention particularly relates to strains of the species Pseudomonas putida wherein the ability to degrade the compounds is on a transferable plasmid.
2. Prior Art
L-tryptophan is an aromatic amino acid which is essential to the growth of certain microorganisms. It is synthesized by various strains of bacteria including strains of Pseudomonas as described in U.S. Pat. Nos. 3,808,101 and 3,849,251.
The prior art has described the use of the amino acid L-tryptophan as a sole carbon source for isolating strains of Pseudomonas from soils. This method is described by H. C. Lichstein and Evelyn L. Oginsky Experimental Microbial Physiology, W. H. Freeman and Company, San Francisco, Experiment 5, pages 23 to 26 (1965). The inventors have used this method for soil bacteria enrichment for many years. The bacteria produced by the method include mixed strains of Pseudomonas, wherein there is a potential for many different species and strains of Pseudomonas in the mixture. This prior art method is utilized in the present invention to isolate the selected strains of Pseudomonas.
The prior art has not thought that strains of Pseudomonas which utilize highly toxic halogenated toluenes or their analogs could be selected because the by-products (from the catabolic pathways) are toxic to the bacteria. This result can be seen from Wigmore, G. J. and Ribbons, D. W., J. Bacteriol., 146 920-927 (June 1981). Various publications have described strains of Pseudomonas which will grow on less toxic substrates but not the halogenated toluenes. These publications include Reineke, W., and H. Knackmuss, Nature, 277:385 (1979); Marinucci, A. C., and R. Bartha, Appl. Environ. Microbiol., 38:811-817 (1979) and Don, R. H., and J. M. Pemberton, J. Bacteriol., 145: 681-686 (1980). Some prior art bacteria are pathogenic.